Electromagnetic device



Manila 5,192?

ELECTROMAGNETIC DEVICE Filed Aug. 16. 1921 zz/ f w Patented Mar. 15, 19 27.

UNITED STATES PA'IYENT OFFICE.

GUSTAF W. ELMEN, OF LEONIA, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COM- IPANY, INCORPORATED, OF NEW YORK, N. Y.,

A CORPORATION-F NEW YORK.

ELECTROMAGNETIC DEVICE.

Application filed August 16, 1921. Serial no. 492 723.

This invention relates to inductive devices and more particularly to devices which are used in electrical systems for transferring the energy by mutual induction from and to electrical circuits. Its object is to improve the efiiciency of such devices.

The invention provides an improved magnetic circuit for magnetic devices of the type referred to and makes use of an improved magnetic material characterized by high premeability, especially at low magnetizing forces, and by low hysteresis losses.

This application is in part a continuation of G. W. Elmen, Serial No. 473,877, filed May 31, 1921, which is a continuation of application Serial No. 111,080, filed July 24, 1916.

Heretofore iron and silicon steel have been employed generally in electromagnetic devices in order to secure high permeability at the forces produced by the currents passing therethrough, while the principal possible rivals of lI'OIl, namely, mckel and cobalt, have found but little application due to their inferior magnetic characteristics. With nickel and cobalt in these respects stands Heuslers allo of aluminum, manganese and copper. t has been found that a composition of about nickel and copper, when tested at low magetizing forces, gives a permeability higher than that of iron alone. It will be seen that with the exception of aluminum, all these metals stand close together in their atomic weights and atomic numbers, and in this specification these five elements, namely, manganese, iron, cobalt, nickel and copper, having the consecutive atomic numbers, 25, 26, 27, 28, 29, will be regarded as belonging to the mag 4 netic group of elements.

The criterion of highpermeability is not the only one to be considered in seeking the best magnetic material for use in electromagnetic devices for transferring the energy of an electric circuit by mutual induction. If the magnetizing forces and the resultant flux are changed rapidly then, for most purposes, the material should exhibit a low hysteresis loss. The developement of eddy currents under these conditions may be obviated to a considerable extent by lamination, but the resistivit of the material is a factor that ma be 0 importance in this connection, the higher the resistivity the more down.

The description hereinafter given is made specific to a repeating coil employing a new magnetic core material which comprises elealthough the desirable characteristics in varying degree are present when the nickel constitutes from around 25% upward. Good commercial grades of these metals are suitable for this purpose. ;The molten composition is poured into a mold and cooled either in the form in which it is ultimately to be used or in a convenient form to be worked over for that purpose. In the latter case it may be swaged or drawn or rolled. When desired to be laminated, some such manner of Working the material to the required form may be necessary.

While 78%% and 2l %'have been mentioned as giving the proportion of the ingredients, nickel and iron, to be employed in making up the improved magnetic material in its preferred form, it will be understood that the proportion may deviate considerably from these figures when nickel and iron are the only ingredients without much change in the] characteristics, and that when there are other ingredients this proportion may not apply. Up to the present time when the only ingredients are nickel and iron, it has been found that a proportion about the same as that named, gives the greatest permeability for low magnetizing forces. ()ther ingredients than nickel and iron may be employed for various purposes, not only to confer high permeability on the product, but for otherobjects; for example, it may be desirable to add chromium for the reason that a comparatively small quantity of this element will cause a decided increase in the resistivity of the composition, and this high resistivity may be a desirable factor to cut down the eddy current losses in the the eddy current loss will be kept' to develop high permeability has been found to be to heat the material to a tern perature that will be suitable for annealing, then to cool at an optimum rate that must be determined by experiment. After the heat treatment the material must be guarded against any considerable strains, in other words, the heat treatment is preferably applied to the material in its ultimate form or shape in. the apparatus in which it is to be use The drawing showsone type of repeating coil. The magnetic core 1 is, provided with a primary winding 2 and a secondary winding 3. An alternating current flowing through the primary windin produces a varying magnetizing force w ich in turn sets up varying lines of magnetic induction within the magnetic core 1.

These changing magnetic fluxes induce an electromotive force in the secondary winding 3 which is proportional at every instant to the rate of change in the flux. The electromotive force induced in the secondary winding 3 will depend upon the number of turns in the primary and secondary windings and also upon the rate of change of the number of lines of flux with in the core. lhe magnitude of the flux is dependent upon the permeability of the material at the magnetizing force produced by the current in the primary winding,

which is used in the core 1. Thus, if air were used instead of iron, the flux would be exactly equal to the magnetizing force no matter what the force might be. If iron is used for the core and a magnetizing force of about H=0.001 C. G. S. units is produced by the current passing through the primary winding 2,the permeability of the iron at this force would be about 250. Silicon steel, on the other hand, would exhibit a permeability of about 500 at this force. 1 r

It has been found that depending upon the percentage composition of the nickeliron composition employed permeabilities ranging from 800 to 5,000 may be secured at a magnetizing'force of about H=0.001 C. G. S. units and at a magnetizing force of rea ers about Hfll C. G. S. units, the crmeability may be as high as 57,000. he use of this magnetic material for the cores of repeating coils and the like, will result in great economy of space on account of the fact that a much smaller amount ofmaterial is required to effect the same result which may be obtained when iron orsilicon steel is used. For example, a standard type of repeating coil used in telephone systems has a silicon steel core which weighs approximately one pound. By substituting a nickel-iron core for the silicon steel core the same inductance may be obtained with a core weighing only two ounces.

- The present invention is, therefore, di-- rected particularly to. the class of electromagnetic devices having a high impedance in which the primary object is to transfer the electrical energy by mutual induction,

utilizing only a small amount of the total current flowing through the circuit.

While the invention has been more particularly described as applied to a repeating coil it is intended to include within the scope of the appended claims, other inductive devices of the transformer type in which it is desired to keep the transformation loss as small as possible.

What is claimedis: p

1. An electromagnetic device having an electrical conductor disposed about a core comprising at least two elements of the magnetic group, one of which is nickel, and having a higher permeability than iron for magnetizing forces of the order of a few tenths of a C. G. S. unit or low.

2. An electromagnetic vdevice having an tilt Mill

electrical conductor disposed about a core comprising at least two elements of the magnetic group, one of which is nickel to the extent of 50% but less than another of which is iron to the extent of at ing a higher permeability than iron for magnetizing forces of the order of a few tenths of a C. G. S. unit or less.

3. An electromagnetic device having a winding designed for currents of the order of those used in signaling, and a core comprising a material having as constitutent elements at least nickel and iron of the least 20% but not more than 35%, and havprimary winding,

ingi as constituent elements at least nickel an iron of the magnetic group of elements, and in which the nickel constitutes within a few per cent of 78.5% of the nickel-iron content, the permeability of said material being greater than for iron at forces of a few tenths of a O. G. 8. unit, such as would be set up in said core by signaling currents in said winding, and the hysteresis loss being less.

5. An electromagnetic device having a a secondary winding and a magnetic core comprising at least two elements of the magnetic roup, one of which is nickel and having a igher permeability than iron for magnetizing forces of the order of a few tenths of a C. G. S. unit or less.

6. An electromagnetic device having a primary winding and a secondary windin both designed for currents of the order oi those used. in signaling, and a core comprising a material having as constituent elements at least nickel and iron of the magnetic roup of elements, and in which the nickel orms at least 25% of the nickel-iron content, the permeability of said material being eater than for iron at forces of a few tent s of a C. G. S. unit,.such as would be set up in said coreby signaling currents in said windings, and the hysteresis loss bein less. 7. An electromagnetic device having a primary winding, a secondary winding and a core comprising an alloy consisting chiefly of nickel and iron in which the nickel component is within a few per cent of 78 570 or thereabouts of the nickel-iron content.

8. A repeating coil for signalling currents having a grimary winding, 8. secondary winding an a core comprising a material consisting' chiefly of nickel and iron, said core having a higher permeability than iron for magnetizing forces of approximately two-tenths of a C. G. S. unit or less. 9. An electromagnetic device having a primary winding and a secondary winding, a magnetic material comprising nickel and iron associated with said windings, said device bein adapated for use in an electrical circuit w en t e magnetizing forces produced by the current therein are of the order of H=0.2 O. G. S. units.

In Witness whereof, I hereunto subscribe my name this 10th day of August, A. D., 1921.

GUSTAF W. ELMEN. 

